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</tr></table><h1 class="title">Event Transitions Example<br /><span class="subtitle"></span>

</h1>

<p>Files:</p>

<ul>

<li><a href="statemachine-eventtransitions-main-cpp.html">statemachine/eventtransitions/main.cpp</a></li>

<li><a href="statemachine-eventtransitions-eventtransitions-pro.html">statemachine/eventtransitions/eventtransitions.pro</a></li>

</ul>

<p>The Event Transitions example shows how to use event transitions, a feature of <a href="statemachine-api.html">The State Machine Framework</a>.</p>

<pre> class Window : public QWidget

{

public:

Window(QWidget *parent = 0)

: QWidget(parent)

{

QPushButton *button = new QPushButton(this);

button->setGeometry(QRect(100, 100, 100, 100));</pre>

<p>The <tt>Window</tt> class's constructors begins by creating a button.</p>

<pre> QStateMachine *machine = new QStateMachine(this);

QState *s1 = new QState();

s1->assignProperty(button, "text", "Outside");

QState *s2 = new QState();

s2->assignProperty(button, "text", "Inside");</pre>

<p>Two states, <tt>s1</tt> and <tt>s2</tt>, are created; upon entry they will assign "Outside" and "Inside" to the button's text, respectively.</p>

<pre> QEventTransition *enterTransition = new QEventTransition(button, QEvent::Enter);

enterTransition->setTargetState(s2);

s1->addTransition(enterTransition);</pre>

<p>When the button receives an event of type <a href="qevent.html#Type-enum">QEvent::Enter</a> and the state machine is in state <tt>s1</tt>, the machine will transition to state <tt>s2</tt>.</p>

<pre> QEventTransition *leaveTransition = new QEventTransition(button, QEvent::Leave);

leaveTransition->setTargetState(s1);

s2->addTransition(leaveTransition);</pre>

<p>When the button receives an event of type <a href="qevent.html#Type-enum">QEvent::Leave</a> and the state machine is in state <tt>s2</tt>, the machine will transition back to state <tt>s1</tt>.</p>

<pre> QState *s3 = new QState();

s3->assignProperty(button, "text", "Pressing...");

QEventTransition *pressTransition = new QEventTransition(button, QEvent::MouseButtonPress);

pressTransition->setTargetState(s3);

s2->addTransition(pressTransition);

QEventTransition *releaseTransition = new QEventTransition(button, QEvent::MouseButtonRelease);

releaseTransition->setTargetState(s2);

s3->addTransition(releaseTransition);</pre>

<p>Next, the state <tt>s3</tt> is created. <tt>s3</tt> will be entered when the button receives an event of type <a href="qevent.html#Type-enum">QEvent::MouseButtonPress</a> and the state machine is in state <tt>s2</tt>. When the button receives an event of type <a href="qevent.html#Type-enum">QEvent::MouseButtonRelease</a> and the state machine is in state <tt>s3</tt>, the machine will transition back to state <tt>s2</tt>.</p>

<pre> machine->addState(s1);

machine->addState(s2);

machine->addState(s3);

machine->setInitialState(s1);

machine->start();

}

};</pre>

<p>Finally, the states are added to the machine as top-level states, the initial state is set to be <tt>s1</tt> ("Outside"), and the machine is started.</p>

<pre> int main(int argc, char **argv)

{

QApplication app(argc, argv);

Window window;

window.resize(300, 300);

window.show();

return app.exec();

}</pre>

<p>The main() function constructs a Window object and shows it.</p>

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